Heretofore, the adhesives used to bond silicone rubber parts or profiles to each other were organopolysiloxane compositions which cure in air at room temperature. The curing time of these compositions is several hours, and the adhesives have low mechanical strength.
British Patent No. 2,049,717 (W. J. Bobear, General Electric Company) discloses inhibitor-containing, platinum-catalyzed silicone rubber compositions for hot-air vulcanization which contain:
(a) An organopolysiloxane having Si-bonded vinyl groups; PA0 (b) an organopolysiloxane having Si-bonded hydrogen; PA0 (c) a platinum catalyst; PA0 (d) an inhibitor containing a radical of the formula --C--O--O--H; and PA0 (e) an organic peroxide having the --C--O--O--C group in the molecule. PA0 (a) An organopolysiloxane containing Si-bonded vinyl groups; PA0 (b) an organopolysiloxane containing Si-bonded hydrogen; PA0 (c) a platinum catalyst which promotes the addition reaction of Si-bonded hydrogen with vinyl groups; PA0 (d) an inhibitor which delays the addition reaction of Si-bonded hydrogen with vinyl groups at room temperature, with the proviso that inhibitors containing a hydroperoxy radical are excluded; and PA0 (e) an organic peroxide, with the proviso that acyl peroxides are excluded.
The organic peroxide (e) is added to the compositions as a curing accelerator, since the hydroperoxy inhibitor (d) is otherwise so effective in these compositions that the compositions only cure on heating to about 540.degree. C. for a longer period than desired for hot-air vulcanization. The addition of the organic peroxide then allows curing of the compositions at 370.degree. C.
The British patent does not disclose the use of inhibitor-containing, platinum-catalyzed silicone rubber compositions as adhesives, nor could their use as adhesives be obvious. The compositions described in the British patent cannot be employed as an adhesive since the compositions described therein only cure at temperatures of 370.C.
Therefore, it is an object of the present invention to provide, as adhesives, an organopolysiloxane composition which can be cured to form elastomers. Another object of the present invention is to provide adhesives for bonding at least two similar or dissimilar readily available organopolysiloxane elastomers to one another. Still another object of the present invention is to provide adhesives for bonding readily available organopolysiloxane elastomer to optionally primed substrates. A further object of the present invention is to provide adhesives having particularly short curing times, high mechanical strength, and adhesion points which are essentially invisible.